Class IV Antiarrhythmics: Calcium channel blocker
This class of antiarrhythmics (drugs for cardiac arrhythmia) are substances that block calcium channels (slow, voltage-dependent L-type channels). This makes it more difficult to trigger excitation in the sinus and AV node and to transfer excitation. They are use dependent and block the channels only if they are open or inactive. They are used for rhythm disturbances originating in the atrium (supraventricular tachycardia). Examples are verapamil, gallopamil and diltiazem.
Further points of attack of antiarrythmics
- Stimulation of the parasympathetic part of the autonomic nervous system: The substances digoxin and digitoxin are used. These are so-called cardiac glycosides. The effect is shown by stimulation of nuclei of the vagus nerve, the main effector of the parasympathetic nervous system, whose nuclei are located in the brain.
Since the parasympathetic nerve at the heart only acts in the area of the atria, its use is explained by cardiac arrhythmias (drugs for cardiac arrhythmias) emanating from the atria (supraventricular tachycardia, atrial fibrillation). Cardiac glycosides must not be administered for disorders emanating from the ventricles (ventricular arrhythmias) because they can then trigger ventricular fibrillation.
- Stimulation of the adenosine receptor: This opens specific potassium channels located in the sinus node. The cell remains unexcitable for longer.
In addition, calcium channels are blocked, which influences the transmission of the AV node. The substance is suitable for seizure-like disorders originating in the atrium (paroxysmal supraventricular tachycardia). The substance must not be administered during an AV block.
- Magnesium inhibits the transmission of excitation in high doses.
- HCN channel blockade: The cells in the sinus node have an additional channel that allows the ions potassium and sodium to pass through. The inhibitor ivabradine is used when beta-blockers cannot be given in patients with angina pectoris.
Side effects
Side effects include agitation, anxiety, danger of tachyarrhythmias.
